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Van NTB, Yen NTP, Nhung NT, Cuong NV, Kiet BT, Hoang NV, Hien VB, Chansiripornchai N, Choisy M, Ribas A, Campbell J, Thwaites G, Carrique-Mas J. Characterization of viral, bacterial, and parasitic causes of disease in small-scale chicken flocks in the Mekong Delta of Vietnam. Poult Sci 2019; 99:783-790. [PMID: 32036978 PMCID: PMC7587710 DOI: 10.1016/j.psj.2019.10.033] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Revised: 10/08/2019] [Accepted: 10/08/2019] [Indexed: 11/28/2022] Open
Abstract
In the Mekong Delta region of Vietnam, small-scale chicken farming is common. However, high levels of disease or mortality in such flocks impair economic development and challenge the livelihoods of many rural households. We investigated 61 diseased small-scale flocks (122 chickens) for evidence of infection with 5 bacteria, 4 viruses, and helminths. Serological profiles (ELISA) were also determined against 6 of these pathogens. The aims of this study were the following: (1) to investigate the prevalence of different pathogens and to compare the probability of detection of bacterial pathogens using PCR and culture; (2) to investigate the relationship between detection of organisms in birds' tissues and the observed morbidity and mortality, as well as their antibody profile; and (3) to characterize risk factors for infection with specific viral or bacterial pathogens. We used PCR to test for viral (viruses causing infectious bronchitis [IB], highly pathogenic avian influenza [HPAI], Newcastle disease, and infectious bursal disease [IBD]) and bacterial pathogens (Mycoplasma gallisepticum, Pasteurella multocida, Avibacterium paragallinarum, and Ornithobacterium rhinotracheale [ORT]). The latter two were also investigated in respiratory tissues by conventional culture. Colisepticemic Escherichia coli was investigated by liver or spleen culture. In 49 of 61 (80.3%) flocks, at least one bacterial or viral pathogen was detected, and in 29 (47.5%) flocks, more than one pathogen was detected. A. paragallinarum was detected in 62.3% flocks, followed by M. gallisepticum (26.2%), viruses causing IBD (24.6%) and IB (21.3%), septicemic E. coli (14.8%), ORT (13.1%), and HPAI viruses (4.9%). Of all flocks, 67.2% flocks were colonized by helminths. Mortality was highest among flocks infected with HPAI (100%, interquartile range [IQR]: 81.6–100%) and lowest with flocks infected with ORT (5.3%, IQR: 1.1–9.0%). The results indicated slight agreement (kappa ≤ 0.167) between detection by PCR and culture for both A. paragallinarum and ORT, as well as between the presence of cestodes and ORT infection (kappa = 0.317). Control of A. paragallinarum, viruses causing HPAI, IBD, and IB, M. gallisepticum, and gastrointestinal helminths should be a priority in small-scale flocks.
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Affiliation(s)
- Nguyen Thi Bich Van
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
| | - Nguyen Thi Phuong Yen
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Nguyen Thi Nhung
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Nguyen Van Cuong
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Bach Tuan Kiet
- Sub-Department of Animal Health, Dong Thap Province, Cao Lanh, Vietnam
| | - Nguyen Van Hoang
- Sub-Department of Animal Health, Dong Thap Province, Cao Lanh, Vietnam
| | - Vo Be Hien
- Sub-Department of Animal Health, Dong Thap Province, Cao Lanh, Vietnam
| | - Niwat Chansiripornchai
- Avian Health Research Unit, Faculty of Veterinary Science, Chulalongkorn University, Thailand
| | - Marc Choisy
- Oxford University Clinical Research Unit, Hanoi, Vietnam; MIVEGEC, IRD, CNRS, University of Montpellier, Montpellier, France
| | - Alexis Ribas
- Department of Zoology and Fisheries, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences, Prague, Czech Republic
| | - James Campbell
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam; Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom
| | - Guy Thwaites
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam; Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom
| | - Juan Carrique-Mas
- Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam; Nuffield Department of Medicine, Oxford University, Oxford, United Kingdom
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Delabouglise A, Nguyen-Van-Yen B, Thanh NTL, Xuyen HTA, Tuyet PN, Lam HM, Boni MF. Poultry population dynamics and mortality risks in smallholder farms of the Mekong river delta region. BMC Vet Res 2019; 15:205. [PMID: 31208467 PMCID: PMC6580564 DOI: 10.1186/s12917-019-1949-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Accepted: 06/04/2019] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Poultry farming is widely practiced by rural households in Vietnam and the vast majority of domestic birds are kept on small household farms. However, smallholder poultry production is constrained by several issues such as infectious diseases, including avian influenza viruses whose circulation remains a threat to public health. This observational study describes the demographic structure and dynamics of small-scale poultry farms of the Mekong river delta region. METHOD Fifty three farms were monitored over a 20-month period, with farm sizes, species, age, arrival/departure of poultry, and farm management practices recorded monthly. RESULTS Median flock population sizes were 16 for chickens (IQR: 10-40), 32 for ducks (IQR: 18-101) and 11 for Muscovy ducks (IQR: 7-18); farm size distributions for the three species were heavily right-skewed. Muscovy ducks were kept for long periods and outdoors, while chickens and ducks were farmed indoors or in pens. Ducks had a markedly higher removal rate (broilers: 0.14/week; layer/breeders: 0.05/week) than chickens and Muscovy ducks (broilers: 0.07/week; layer/breeders: 0.01-0.02/week) and a higher degree of specialization resulting in a substantially shorter life span. The rate of mortality due to disease did not differ much among species, with birds being less likely to die from disease at older ages, but frequency of disease symptoms differed by species. Time series of disease-associated mortality were correlated with population size for Muscovy ducks (Kendall's coefficient τ = 0.49, p-value < 0.01) and with frequency of outdoor grazing for ducks (τ = 0.33, p-value = 0.05). CONCLUSION The study highlights some challenges to disease control in small-scale multispecies poultry farms. The rate of interspecific contact and overlap between flocks of different ages is high, making small-scale farms a suitable environment for pathogens circulation. Muscovy ducks are farmed outdoors with little investment in biosecurity and few inter-farm movements. Ducks and chickens are more at-risk of introduction of pathogens through movements of birds from one farm to another. Ducks are farmed in large flocks with high turnover and, as a result, are more vulnerable to disease spread and require a higher vaccination coverage to maintain herd immunity.
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Affiliation(s)
- Alexis Delabouglise
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, Millenium Sciences Complex, Pollock road, University Park, PA, 16802, USA.
| | - Benjamin Nguyen-Van-Yen
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,École Normale Supérieure, CNRS UMR 8197, 46 rue d'Ulm, Paris, France
| | - Nguyen Thi Le Thanh
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam
| | - Huynh Thi Ai Xuyen
- Ca Mau sub-Department of Livestock Production and Animal Health, Ca Mau, Vietnam
| | - Phung Ngoc Tuyet
- Ca Mau sub-Department of Livestock Production and Animal Health, Ca Mau, Vietnam
| | - Ha Minh Lam
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,Center for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Maciej F Boni
- Center for Infectious Disease Dynamics, Department of Biology, Pennsylvania State University, Millenium Sciences Complex, Pollock road, University Park, PA, 16802, USA.,Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam.,Center for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
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Nguyen LT, Stevenson MA, Firestone SM, Sims LD, Chu DH, Nguyen LV, Nguyen TN, Le KT, Isoda N, Matsuno K, Okamatsu M, Kida H, Sakoda Y. Spatiotemporal and risk analysis of H5 highly pathogenic avian influenza in Vietnam, 2014-2017. Prev Vet Med 2019; 178:104678. [PMID: 31113666 DOI: 10.1016/j.prevetmed.2019.04.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 03/10/2019] [Accepted: 04/13/2019] [Indexed: 10/27/2022]
Abstract
The aim of this study was to describe the spatiotemporal distribution of H5 HPAI outbreak reports for the period 2014-2017 and to identify factors associated with H5 HPAI outbreak reports. Throughout the study period, a total of 139 outbreaks of H5 HPAI in poultry were reported, due to either H5N1 (96 outbreaks) or H5N6 (43 outbreaks) subtype viruses. H5N1 HPAI outbreaks occurred in all areas of Vietnam while H5N6 HPAI outbreaks were only reported in the northern and central provinces. We counted the number of H5N1 and H5N6 outbreak report-positive districts per province over the four-year study period and calculated the provincial-level standardized morbidity ratio for H5N1 and H5N6 outbreak reports as the observed number of positive districts divided by the expected number. A mixed-effects, zero-inflated Poisson regression model was developed to identify risk factors for outbreak reports of each H5N1 and H5N6 subtype virus. Spatially correlated and uncorrelated random effects terms were included in this model to identify areas of the country where outbreak reports occurred after known risk factors had been accounted-for. The presence of an outbreak report in a province in the previous 6-12 months increased the provincial level H5N1 outbreak report risk by a factor of 2.42 (95% Bayesian credible interval [CrI] 1.27-4.60) while 1000 bird increases in the density of chickens decreased provincial level H5N6 outbreak report risk by a factor of 0.65 (95% CrI 0.38 to 0.97). We document distinctly different patterns in the spatial and temporal distribution of H5N1 and H5N6 outbreak reports. Most of the variation in H5N1 report risk was accounted-for by the fixed effects included in the zero-inflated Poisson model. In contrast, the amount of unaccounted-for risk in the H5N6 model was substantially greater than the H5N1 model. For H5N6 we recommend that targeted investigations should be carried out in provinces with relatively large spatially correlated random effect terms to identify likely determinants of disease. Similarly, investigations should be carried out in provinces with relatively low spatially correlated random effect terms to identify protective factors for disease and/or reasons for failure to report.
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Affiliation(s)
- Lam Thanh Nguyen
- Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, North 18, West 9, Kita-ku, Sapporo, Hokkaido, 060-0818, Japan; Department of Veterinary Medicine, College of Agriculture, Can Tho University, Campus II, 3/2 Street, Ninh Kieu, Can Tho, Viet Nam
| | - Mark A Stevenson
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia.
| | - Simon M Firestone
- Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Leslie D Sims
- Asia Pacific Veterinary Information Services, Montmorency, Victoria, 3094, Australia
| | - Duc Huy Chu
- Department of Animal Health, Ministry of Agriculture and Rural Development, Ha Noi, Viet Nam
| | - Long Van Nguyen
- Department of Animal Health, Ministry of Agriculture and Rural Development, Ha Noi, Viet Nam
| | - Tien Ngoc Nguyen
- Department of Animal Health, Ministry of Agriculture and Rural Development, Ha Noi, Viet Nam
| | - Kien Trung Le
- Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, North 18, West 9, Kita-ku, Sapporo, Hokkaido, 060-0818, Japan
| | - Norikazu Isoda
- Research Center for Zoonosis Control, Hokkaido University, North 20, West 10, Kita-ku, Sapporo, Hokkaido, 001-0020, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, North 20, West 10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
| | - Keita Matsuno
- Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, North 18, West 9, Kita-ku, Sapporo, Hokkaido, 060-0818, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, North 20, West 10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
| | - Masatoshi Okamatsu
- Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, North 18, West 9, Kita-ku, Sapporo, Hokkaido, 060-0818, Japan
| | - Hiroshi Kida
- Research Center for Zoonosis Control, Hokkaido University, North 20, West 10, Kita-ku, Sapporo, Hokkaido, 001-0020, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, North 20, West 10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
| | - Yoshihiro Sakoda
- Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, North 18, West 9, Kita-ku, Sapporo, Hokkaido, 060-0818, Japan; Global Institution for Collaborative Research and Education, Hokkaido University, North 20, West 10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan.
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Molia S, Grosbois V, Kamissoko B, Sidibe MS, Sissoko KD, Traore I, Diakite A, Pfeiffer DU. Longitudinal Study of Avian Influenza and Newcastle Disease in Village Poultry, Mali, 2009-2011. Avian Dis 2017; 61:165-177. [PMID: 28665735 DOI: 10.1637/11502-092616-reg.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Newcastle disease (ND) is endemic in West Africa, which has also experienced outbreaks of highly pathogenic avian influenza (AI) H5N1 since 2006. We aimed to estimate the prevalence and incidence of AI and ND in village poultry in Mali and to identify associated risk factors. A longitudinal serologic study was conducted between November 2009 and February 2011 using ELISA commercial kits to detect antibodies. Sera (5963) were collected from 4890 different poultry. AI was rare, with a seroprevalence of 2.9% (95% confidence interval [CI] 2.3-3.5) and a seroincidence rate of 0.7 birds per 100 bird-months at risk (95% CI 0.4-1.0). AI antibodies were short lived, with a seroreversion rate of 25.4 birds per 100 bird-months at risk (95% CI 19.0-31.7). Risk factors for AI were limited: temporal variation occurred, but proximity to a water body was a risk factor only when large populations of wild waterbirds were present. ND was very common, with seroprevalence of 68.9% (95% CI 61.9-76.0) and a seroincidence rate of 15.9 birds per 100 bird-months at risk (95% CI 11.9-19.8). ND seroreversion rate was 6.2 birds per 100 bird-months at risk (95% CI 3.6-8.9). Regarding risk factors for ND, temporal variations occurred, and ND was more likely to be present in the Sudanian agro-ecological zone than in the Sahelian zone, in chickens than in other species, in flocks with higher numbers of Guinea fowl, and in flocks that had access to a waterbody. Control efforts would benefit from further increasing the ND vaccination coverage of village poultry, although this was already quite high (54.9%) for an African country. Seroconversion seemed satisfactory in vaccinated poultry, since 90.0% (95% CI 87.6-92.4) of these had ND antibodies. Further research should investigate the apparent lack of an epidemiologic role of domestic ducks for AI in Mali (unlike in Southeast Asia) and the potential role of Guinea fowl as a reservoir for ND.
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Affiliation(s)
- Sophie Molia
- A CIRAD, Centre Régional de Santé Animale, BP1813, Sotuba, route de Koulikoro, Bamako, Mali.,B CIRAD, UPR AGIRs, Campus international de Baillarguet, F-34398 Montpellier, France
| | - Vladimir Grosbois
- B CIRAD, UPR AGIRs, Campus international de Baillarguet, F-34398 Montpellier, France
| | - Badian Kamissoko
- C Laboratoire Central Vétérinaire, BP 2295, Km 8, route de Koulikoro, Bamako, Mali
| | | | | | - Idrissa Traore
- C Laboratoire Central Vétérinaire, BP 2295, Km 8, route de Koulikoro, Bamako, Mali
| | - Adama Diakite
- C Laboratoire Central Vétérinaire, BP 2295, Km 8, route de Koulikoro, Bamako, Mali
| | - Dirk Udo Pfeiffer
- E VEEPH Group, Royal Veterinary College, North Mymms, Hertfordshire, AL9 7TA, United Kingdom
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Meyer A, Dinh TX, Nhu TV, Pham LT, Newman S, Nguyen TTT, Pfeiffer DU, Vergne T. Movement and contact patterns of long-distance free-grazing ducks and avian influenza persistence in Vietnam. PLoS One 2017. [PMID: 28632789 PMCID: PMC5478089 DOI: 10.1371/journal.pone.0178241] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Presence of ducks, and in particular of free-grazing ducks, has consistently been shown to be one of the most important risk factors for highly pathogenic avian influenza outbreaks which has compromised poultry production in South-East Asia since the early 2000s and continues to threaten public health, farmers’ livelihood and food security. Although free-grazing duck production has been practised for decades in South-East Asia, there are few published studies describing this production system, which is suspected to play an important role in the maintenance of avian influenza viruses. This study aimed at describing quantitatively the long-distance free-grazing duck production system in South Vietnam, characterising the movement and contact patterns of the duck flocks, and identifying potential associations between farming practices, movement and contact patterns and the circulation of avian influenza viruses. We conducted interviews among stakeholders involved in the free-grazing duck production system (duck farmers, transporters and rice paddy owners) in combination with a virological cross-sectional survey in South Vietnam. Results show that both direct and indirect contacts between free-grazing duck flocks were frequent and diverse. The flocks were transported extensively across district and province boundaries, mainly by boat but also by truck or on foot. A third of the investigated flocks had a positive influenza A virology test, indicating current circulation of avian influenza viruses, but none were positive for H5 subtypes. The age and size of the flock as well as its location at the time of sampling were associated with the risk of influenza A circulation in the flocks. These findings should be considered when developing risk assessment models of influenza virus spread aimed at informing the development of improved biosecurity practices leading to enhanced animal health, sustainable animal production and reliable income for farmers.
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Affiliation(s)
- Anne Meyer
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, London, United-Kingdom
- * E-mail:
| | | | - Thu Van Nhu
- National Institute for Animal Sciences, Hanoi, Vietnam
| | - Long Thanh Pham
- Department of Animal Health, Ministry of Agriculture and Rural Development, Hanoi, Vietnam
| | - Scott Newman
- Emergency Centre for Transboundary Animal Diseases, Food and Agriculture Organization of the United Nations, Hanoi, Vietnam
| | - Thuy Thi Thanh Nguyen
- Emergency Centre for Transboundary Animal Diseases, Food and Agriculture Organization of the United Nations, Hanoi, Vietnam
| | - Dirk Udo Pfeiffer
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, London, United-Kingdom
- School of Veterinary Medicine, City University of Hong Kong, Kowloon, Hong Kong SAR, China
| | - Timothée Vergne
- Veterinary Epidemiology, Economics and Public Health Group, Royal Veterinary College, London, United-Kingdom
- MIVEGEC (Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle) Group, Institut de Recherche pour le Développement (IRD-224, CNRS-5290, Université de Montpellier 2), Montpellier, France
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Cuong NV, Truc VNT, Nhung NT, Thanh TT, Chieu TTB, Hieu TQ, Men NT, Mai HH, Chi HT, Boni MF, van Doorn HR, Thwaites GE, Carrique-Mas JJ, Hoa NT. Highly Pathogenic Avian Influenza Virus A/H5N1 Infection in Vaccinated Meat Duck Flocks in the Mekong Delta of Vietnam. Transbound Emerg Dis 2016; 63:127-35. [PMID: 26748550 PMCID: PMC4819680 DOI: 10.1111/tbed.12470] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Indexed: 11/26/2022]
Abstract
We investigated episodes of suspected highly pathogenic avian influenza (HPAI)-like illness among 12 meat duck flocks in two districts in Tien Giang province (Mekong Delta, Vietnam) in November 2013. In total, duck samples from 8 of 12 farms tested positive for HPAI virus subtype A/haemagglutinin 5 and neuraminidase 1 (H5N1) by real-time RT-PCR. Sequencing results confirmed clade of 2.3.2.1.c as the cause of the outbreaks. Most (7/8) laboratory-confirmed positive flocks had been vaccinated with inactivated HPAI H5N1 clade 2.3.4 vaccines <6 days prior to onset of clinical signs. A review of vaccination data in relation to estimated production in the area suggested that vaccination efforts were biased towards larger flocks and that vaccination coverage was low [21.2% ducks vaccinated with two shots (range by district 7.4-34.9%)]. The low-coverage data, the experimental evidence of lack of cross-protection conferred by the currently used vaccines based on clade 2.3.4 together with the short lifespan of meat duck flocks (60-70 days), suggest that vaccination is not likely to be effective as a tool for control of H5N1 infection in meat duck flocks in the area.
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Affiliation(s)
- N V Cuong
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
| | - V N T Truc
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
- University of Science, Ho Chi Minh City, Vietnam
| | - N T Nhung
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
| | - T T Thanh
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
| | - T T B Chieu
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
| | - T Q Hieu
- Sub-Department of Animal Health, Tien Giang Province, Vietnam
| | - N T Men
- Sub-Department of Animal Health, Tien Giang Province, Vietnam
| | - H H Mai
- Sub-Department of Animal Health, Tien Giang Province, Vietnam
| | - H T Chi
- Sub-Department of Animal Health, Tien Giang Province, Vietnam
| | - M F Boni
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, UK
| | - H R van Doorn
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, UK
| | - G E Thwaites
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, UK
| | - J J Carrique-Mas
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, UK
| | - N T Hoa
- Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Hospital for Tropical Disease, Ho Chi Minh City, Vietnam
- Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, UK
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